Method of applying metallic sheathing to metallic cores



June 1 ,1926. 1,586,888

- G. W. ELMEN METHOD OF APPLYING METALLIC SHEATHING T0 METALLIC CORES Filed June 25. 1925 Patented June 1, 1926.

- UNITED STATES PATENT OFFICE.

GUSTAF W. ELMEN, OF LEONIA, NEW JERSEY, ASS IGNOR TO WESTERN ELECTRIC COM- PANY INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF APPLYING METALLIC SHEATHING TO METALLIC CORES.

Application filed June 25, 1923. Serial No. 647,477.

This invention relates to the application of metallic wrappings to metallic cores, such, for example as magnetic wrappings to electrical conductors and particularly to the manufacture of continuously loaded signal-/ core, such as a magnetic sheathing on an electrical conductor.

Another object of the invention is to continuously load signaling conductors whereby a predetermined permeability at low magnetizing forces in the magnetic material may be realized. a

In carrying out the above noted. object there is preferabl applied to the signaling conductor or con uctors a magnetic sheath in the form of a layer or layers of wire or tape wound spi ally thereon. The magnetic material which it is preferred to use, however, is the nickel iron alloy described in the U. S. application of G. W. Elmen, Serial No. 473,877, filed May 31, 1921. This material has the requisite of high permeability only when properly heat treated, and not subsequently subjected to excessive strain. It was found that the strains set up in this '0 loading material by applying it to the conductor were suflicient to lower the permeability and that this difilculty could be overcome by applying proper heat treatment to the loaded conductor. See the Elmen applica tion referred to above and also application, Serial No. 557 ,928, filed May 2, 1922, of the same inventor. I I

Difiiculty has been experienced, however,

in obtaining the desired high value Ofpermeability in the loading material at low magnetizing forces when. the above described process is used.' According to the present invention, the taped conductor, before the final treatment, is subjected to a swaging,

Q which servesto slightly'reduce the diameter of the conductor without correspondingly reducing the diameter of the taping material since the conductor,-.which is of copper, is much softer than the taping material, which is very hard, and as pointed; out in the above mentioned applications, is preferably composed of about 78% per cent nickel and 21 per cent iron. The tape is therefore made to embrace the conductor loosely, it

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being found that this looseness prevents the reduction of permeability which otherwise subsequently occurs. The invention is independent of any theory which may be advanced to account for the benefit derived,

' and the following statement is therefore made merely as a possible explanation of the action discovered without intending thereby to limit the invention in any way. This beneficial action was at first ascribed to a freedom of strain in' the tape during cooling subsequent to the heat treatment of the wrapped conductor, the cooling of the tape being more rapid than that in theconductor because of its more intimate contact with the cooling medium and therefore contracting more rapidly. Recent investlgations, however, indicate that the benefit may result from the heat insulating property of the layer of air-in the space introduced between the conductor and the magnetic wrapping by swag- This layer of heat insulation may reduce the flow of heat from the conductor to the tape during the cooling process thereby permitting the tape to be more readily cooled at the rate which is necessary to obtain high permeability. The cooling of the conductor may in that case be affected by transfer of heat longitudinally in the conductor rather than laterally to the magnetic -wrapping. It is not unlikely that each of these actions plays a part in the finalresult.

For further details of the invention reference may be made to the drawings, wherein Fig. 1 is a .side elevation illustrating the taped conductor, with a conventional swag ing device shown in cross-section. Fig. 2 is an end elevation of Fig. 1. Fig. 3 illustrates the taped conductor, a portion of which has been ,swaged and a portion of'which has not, the parts being magnified several times.

Referring in detail to the drawings, the

conductor 1 is shown as" a solid copper conductor covered with a wrapping. 2 of permalloy tape of the composition above noted.

By way of example, the conductor 1 may-be 180 mils. in diameter and the tape may be 6 mils. thick and ,4;inch wide; Thetensio'n on the tape 2during the process of wrapping it, as described in the above noted applica 'tions, should, under -the;conditions there stated, be-about six ounces. -This"gives a is so close that if a taped conductor .is

wrapping of the tape on the conductor which grasped by the hands it will be found very diflicult, if not impossible, to make any appreciable separation between abutting edges, such as 3 and 4. Such a closely taped conductor, however, has the defect above noted of a low and variable permeability.

This defect has been avoided, according to the present invention, by passin'g the closely taped conductor through a swaging machine, the die blocks 5 and 6 of which are illustrated in the drawings. In the case of use of a conductor of the above noted dimensions, it has been found sufiicient to swage the taped conductor only to such an extent that the diameter of the core or conductor 1 is reduced from 3 to 6 mils. As above pointed out, this swaging inappreciably changes the dimensions of the tape due to thefact that it is of much harder material than the conductor 1, on which it is wrapped. v

In Fig. 3, the portion 7 illustrates the appearance of the conductor 1 prior to swaging, the tape 2 being'showmas lying closely thereagainst, while the portion 8 shows, the reduction in the'diameter of the conductor 1 due to swaging, the internal diameter of the cylinder formed by the tape 2 being several mils larger than the diameter of the portion 8. With the taped conductor, the dimensions of which are above given, it has been found that good results may be obtained by passing. it through the swaging machine at a rate of from ten to fifteen feet per minute.

The magnetic tape is then subjected to a heat treatment, preferably by passing the taped conductor througha suitable furnace at sultable rate, and cooling the conductor at a proper rate after it emerges from the furnace. This heat treatment per se forms no part of the present invention and has beendescribed and claimed in application 557,928, above noted. According to present practice this heat treatment comprises glggtln the tape to a temperature of about for a few minutes to insure a uniform temperature throughout, then'cooling. slowly finally cooling from that temperature more "rapidly but at a definite ratedependent upon the ratio of nickel to iron in the alloy. This ratecan be easily determined by'trials.

A, convenient method of securing the desired rate of. cooling has been found 'to be a rapidwithdrawing of the material from the urnace. when it has for some. time been t? QPebove a te p ature of 850? Qjnto.

., maintaining it at that temperature a blast of'a-ir or inert gas which is controlled to secure the desired rate of cooling. The necessary cooling will always be at a rate intermediate to that required for annealing and that at which such internal strains would be set up as to lower the permeability below the desired value.

The taped conductor maybe suitabl insulated by having a coating of ru ber, gutta percha or the like applied thereto and employed as a submarine cable.

What is claimed is v 1. The method of treating a metallic conductor having a'metallic wrapping thereon which comprises swaging the wrapped conductor to cause said wrapping to embrace said conductor loosely.

2. The method which comprises swaging an electrical conductor having a magnetic covering thereon whereby the covering loosely embraces the conductor.

3. The method which comprises wrapping magnetic material on, an electrical conductor, swaging the wrapped conductor, heat ing the wrapped conductor above the magnetic transition temperature of the magnetic material,and cooling it at a rate to 'give said material high permeability when cooled.

4. The method of loosening a metallic sheathing on a metallic core which comprises swaging the sheathed core.

5. The method of treating a composite conductor comprising a metallic core element and a magnetic sheathing element which comprises changing the'diameter of at least one of said elements, whereby the sheathing is loosened;

6. The method of loosenin g a magnetic sheathin g on a metallic core which comprises mechanically reducing the diameter of the core without removing the sheathing.

7. The method of loosening a metallic sheathing element on a metallic core element which comprises applying force laterally to said sheathing element to change the diameter of one of said elements.

8. The method 'of loosening a metallic wrapping on a metallic core which comprises applying force laterally to said wrap- 9. The method which comprises wrapping magnetic material on .an electrical conductor, subsequently causing said wrapping to become loose on said conductor by the application of force to said wrapping, heating the loosely wrapped conductor above the ma etic transition temperature of the magnetic material, and cooling it at a rate to give said material high permeability when cooled. In witness whereof, I hereunto subscribe my name. this 16th.day of June. A.' 1),, 1923} GUSTAF, 

